| The pervaporation separation of bio-fuels from fermentation broths is a promising method to solve the product inhibition problem with lower energy consumption.The key point for the industrialization of pervaporation in this field is the development of membranes and membrane materials with both high permeation flux and permselectivity.In this thesis,Polyvinylidene fluoride(PVDF)porous membranes were prepared by phase inversion method.The pore structure of porous membranes were regulated by changing the PEG concentration in membrane casting solution.The micro-structure of PVDF membrane and separation performance for ethanol/water mixtures by pervaporation were investigated.It was found that as PEG concentration increased,both separation factor and permeation flux increased at first,and then decreased.The maximum value of separation factor reached as high as 5.2,with the flux of 19.1kg/(m2·h).The comprehensive separation performance of PVDF membranes achieved the similar level as that of PDMS/ceramic composite membrane.Dodecyl phenyl POSS/polydimethylsiloxane(D-POSS/PDMS)filled composite membranes were preparaed with PVDF porous membrane as support layer.Based on SEM characterization it was found that D-POSS and PDMS combined closely,and with the increase of the D-POSS loading,the membrane surface appeared rod-shaped particle aggregates.The thermal stability of PDMS membrane in the range of high temperature,melting temperature and crystallization temperature were improved by the addition of DPOSS particles.In the pervaporation experiments for separation of organic/water,it was discovered when the D-POSS loding was up to 2.5wt%,the separation factor for ethanol/water and n-butanol/water reached the maximum value.The separation factor for acetone/water reached the peak value as POSS loading was 7.5wt%.The separation factor and permeation flux of ethanol/water solution,n-butanol/water solution and acetone/water solution reached 9.5 and 530 g/(m2·h),29 and 470 g/(m2·h),24 and 600 g/(m2·h),respectively.With the increase of operation temperature,the separation factor of ethanol/water decreased,and permeate flux increased gradually.The separation factor acetone/water increased at first,and then decreased,while permeate flux increased gradually.As the feed concentrationincreased,the separation factor first increased and then decreased,with permeate flux increasing continuously.A novel cross-linker octa[(trimethoxysilyl)ethyl]-POSS(OPS)was firstly prepared via hydrosilylation reaction.And then the crosslinking type OPS/PDMS hybrid membraneswere prepared and characterized.It was found that the surface of hybrid membrane was smooth,and no particle aggregates was found with low OPS loading.Along with the increase of OPS loading,self-condensed POSS particles emerged on the membrane surface.The OPS/PDMS hybrid membranes were applied to recovery organic solvent from aqueous solution by pervaporation.The effect of concentration of casting solution,the viscosity of PDMS and the OPS loading on pervaporation performance was investigated.It was discovered that the separation factor for ethanol/water,methanol/water and acetone/water was significantly improved with the incorporation of OPS particles.The maximum value of separation factor was 14.6,9.8 and 48,respectively,which was far higher than that of pure PDMS membrane,which was 8.1,8.5 and 37.3,respectively.With the increase of OPS loading,permeation flux showed increasing trend.OPS/PDMS hybrid membrane showed the anti-trade-off phenomenon in multiple separation system,which provided a new research idea to break the permeation flux-separation factor mutual constraining bottleneck.With the increase of OPS loading,the separation factor of OPS/PDMS hybrid membrane for phenol/water solution decreased,but the permeation flux increased significantly,which indicated that the applicability of the OPS/PDMS was restricted in the mixtures with organics of large molar volume. |
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